Recently, printing apparatuses using inkjet recording method, such as inkjet printers and inkjet plotters, have been widely used in not only printers for general consumers but also industrial purposes of color filter manufacturing, such as for electronic circuit formation and liquid crystal displays, and organic EL display manufacturing.
In the inkjet printing apparatus, liquid discharge heads for discharging liquid are mounted as a printing head. As this type of print head, thermal head method and piezoelectric method are generally known. That is, in the thermal head method, a heater as a pressing means is installed in an ink passage filled with ink, and the ink is heated and boiled by the heater. The ink is pressed by air bubbles occurred in the ink passage, and is then discharged as liquid drops through ink discharge pores. In the piezoelectric method, a part of the ink passage filled with ink is bendingly displaced by a displacement element. The ink in the ink passage is mechanically pressed and is discharged as liquid drops through the ink discharge pores.
The liquid discharge head can employ either serial method or line method. That is, with the serial method, recording is carried out while the liquid discharge head is moved in a direction (a main scanning direction) orthogonal to a transport direction of a recording medium (a sub scanning direction). With the line method, recording is carried out on a recording medium transported in the sub scanning direction in a state in which a liquid discharge head being longer in the main scanning direction than a recording medium is fixed. The line method has an advantage of permitting high speed recording because unlike the serial method, there is no need to move the liquid discharge head.
Even the liquid discharge head of either the serial method or the line method is required to increase the density of the liquid discharge pores for discharging the liquid drops which are formed in the liquid discharge head, in order to print the liquid drops with high density.
For example, there is known a liquid discharge head that is configured by laminating a passage member including a manifold (common passage) and liquid discharge pores connected from the manifold via a plurality of liquid pressing chambers, and an actuator unit having a plurality of displacement elements respectively disposed so as to cover the liquid pressing chambers (refer to, for example, patent document 1). In this liquid discharge head, the liquid pressing chambers respectively connected to the plurality of liquid discharge pores are arranged in a matrix shape, and the displacement elements of the actuator unit arranged to cover the liquid pressing chambers are displaced, thereby constituting a plurality of linear liquid discharge pore rows parallel to each other. Ink is discharged from the liquid discharge pores arranged at equal intervals in one direction so as not to be overlapped with each other in a direction orthogonal to the one direction, thus permitting printing at a resolution of 600 dpi in the main scanning direction and at a resolution of 600 dpi in the sub scanning direction.